An imidazo[1,2-b]pyridazine compound is useful as an intermediate of pharmaceuticals and pesticides. For example, 2,6-dichloroimidazo[1,2-b]pyridazine is an important compound as an intermediate of sulfonylurea herbicides (e.g. U.S. Pat. No. 5,017,212 and U.S. Pat. No. 4,994,571). As processes for producing 2,6-dichloroimidazo[1,2-b]pyridazine, a process comprising reacting 3-imino-6-chloro-2,3-dihydropyridazine-2-acetic acid with phosphorus oxychloride has been known (e.g. JP patent No. 2863857).